A conventional glass melting furnace shown in FIG. 13 includes: a batch introducing port 101 for introducing a glass batch into a melting bath 100 in the furnace; a plurality of combustion ports 102 respectively communicated with combustion burners not shown in the figure; and a derivation port 103 for introducing molten glass out from the melting bath 100. At a position outside the furnace corresponding to the batch introducing port 101, a batch charger 104 is placed for charging a glass batch into the melting bath 100 from the batch introducing port 101 (see Patent Literature 1, for example).
In another conventional glass melting furnace shown in FIG. 14, the batch introducing ports 101, 101 and the combustion ports 102, 102 are provided at horizontally symmetrical positions, respectively, in an upstream region of the melting bath 100, and the batch chargers 104 are provided at positions outside the furnace corresponding to the batch introducing ports 101, respectively.
In each of the above-described glass melting furnaces, an image-capturing device 105 is provided at a position above a downstream region of the melting bath 100. The image-capturing device 105 is to capture an image of an entire liquid surface of the molten glass filled in the melting bath 100 from an obliquely upward position, and the image obtained at the image-capturing device 105 is shown on a monitoring television 106. An operator manually adjusts the amount of the glass batch to be charged by the batch charger 104 while looking at the image on the monitoring television 106 to monitor the charging state of the glass batch into the melting bath 100.